When solid ammonium nitrate dissolves in water, the solution becomes cold. This is the basis for an instant ice pack. When 3.21 g of solid NH4NO3 dissolves in 50.0 g of water at 24.9 C in a calorimeter, the temperature decreases to 20.3 C. Calculate the value of q for this reaction and explain the meaning of its arithmetic sign. O q would be (+) and the reaction is endothermic. O q would be (+) and the reaction is exothermic. O q would be (-) and the reaction is endothermic. O q would be (-) and the reaction is exothermic